Why LHC?

Tara Shears, University of Liverpool

To understand the universe …

Fundamental particles → atoms → stars and galaxies

NOWInvestigate with astrophysics,

using telescopes

BIG BANGInvestigate with

particle physics, usingparticle accelerators.

LHC is key.

.. and what it is made of.

nice …

BUT

? Massup

down

e

e

charm

strange

top

bottom

qu

ark

sle

pto

ns

? matterBig Bang: equal amounts of matter and antimatter created

Now: we (matter) exist

Why?

anti

? 96% of the universe?

How LHC helpsLHC: creates fundamental particles in

proton beam collisions Experiments: take 3D digital snapshots

of particles produced in collisionsComputers: reconstruct and identify

particles detected in experimentTheory: infer which fundamental

particles were originally created in collision

Repeat ……….

Higgs; starting from this event…

We look for this “signature”Selectivity: 1 in 1013

Like looking for 1 person in 1000 world populations

Or for a needle in 20 million haystacks!

making sense of the data

• 40,000,000 proton-proton collisions/second

• ~100,000,000 electronic channels

• 0.0002 Higgs per second

HOW do we find anything?

Distributed Computing Solution – Grid

Concorde(15 Km)

Balloon(30 Km)

CD stack with1 year LHC data!(~ 20 Km)

Mt. Blanc(4.8 Km)

…. a needle in 20 million haystacks!

LHC produces enough data to fill 14 million cds / year (1,000,000 times world annual book production!!)

Estimated we need 100,000 computers to analyse it all …..

grid!

> 5000 computers at 17 sites in UK

> 1 million computing jobs ran last year

What’s out there ….

?……… wait and see what LHC tells us.

Extra dimensions?

Black holes?Higgs

Particles?

Strings?